Yes, another alternator thread

Alright, so tonight my alternator went out on me. Will be changing it tomorrow along with picking up a new battery just because I like going over the top. Been trying to read alot of the threads already on here, but from a mix of alcohol and having never done an alternator swap before, I'm a little lost.

I'd like to upgrade it to the 145a alternator. But what's the big3? I've seen lots of posts about it, not sure if I'm just not catching what it is exactly or what. Only thing I've really noticed is going to a 0/1ga wire to carry the power it truly needs to the battery...

If somebody could spell it out for me in lamens terms it would be greatly appreciated. This car is currently my DD and I can't go without it. Plus I hate not having my baby in perfect working condition.